Phytoplankton integrated multiscale monitoring in the English Channel and North Sea:Automated/high throughput approaches for characterizing changes in phytoplankton assemblies and Harmful Algal Blooms

Phytoplankton integrated observations combine innovative automated/high throughput approaches at high spatial and temporal resolution, to decipher intricate community dynamics. For more than a decade, these techniques have been deployed on a variety of monitoring networks and platforms, dedicated research surveys, fixed stations and moorings and measurements of opportunity, supported by national or international projects. The eastern English Channel and southern North Sea show significant connectivity to adjacent ocean and seas, strong hydrodynamics and are submitted to high riverine inputs and anthropogenic pressure, leading to high productivity and recurring phytoplankton blooms, including some Harmful Algal Blooms-HABs of potential impact on marine food webs, human health and economy. Automated/high throughput approaches provide information on the distribution and dynamics of phytoplankton functional groups (automated flow cytometry) and main taxa (imaging, metabarcoding), community changes, and productivity (variable fluorometry), at high spatial and/or temporal resolution, assigning bloom states and pelagic habitat characteristics based on physical, biogeochemical, and biological variables. In addition to presenting updated results on integrated monitoring, we discuss the relevance of implementing some of these techniques to follow spatial and temporal variability of marine coastal ecosystems and tracking some HABs at different spatial and temporal scales. We underline the importance of ongoing advances in the harmonization of operational practices, data pipelines, automated treatment and analytical and synthesis tools that should allow the inclusion of automated/high throughput data into integrated modelling, building scenarios of ecological trends in coastal marine ecosystems under multiple local to global pressures.